This invention relates to a seal arrangement between an outdrive unit and a hull of a vessel such as a sailing boat.
The applicant's U.K. Pat. No. 1,569,661 (sealing date Aug. 20, 1981) has disclosed a sealing arrangement shown in FIG. 1, wherein an outdrive unit 1 comprising an upper unit 2 and a lower unit 3 is shown in vertical section. An end of an input shaft 4 arranged in the upper unit 2 is connected to an engine (not shown), and the other end of the shaft 4 is connected to a drive shaft 5 through a dog clutch mechanism 6 operable between forward, neutral and reverse positions. The drive shaft 5 is connected to a propeller shaft 7 through a bevel gear mechanism 8 arranged in the lower end of the lower unit 3.
The outdrive unit 1 passes through an opening 10 in a hull 9 of a vessel, and is installed on an installation bed 11 of the hull 9 by means of pairs of brackets 12 with vibration isolating rubbers 13 or other vibration-proof means therebetween. The lower unit 3 projects downward and out of the hull 9 through the opening 10. An annular seal flange 14 is secured to the bed 9 by bolts (not shown). An outer edge of an annular rubber diaphragm seal 15 is pinched and secured between the flange 14 and the bed 9. The inner edge of the seal 15 is pinched and secured between the upper unit 2 and the lower unit 3. The seal 15 covers and seals the opening 10. A radially middle portion 15a of the seal 15 is bent and projects upward, whereby flexibility and damping effect are increased.
The radially inner portion of the flange 14 is situated above the diaphragm seal 15 and projects toward the outdrive unit 1. The seal flange 14 has a groove 14a at the inner edge thereof, into which a radially outer portion of a ring seal 16 having an inverse U-shaped section is fitted. The radially inner portion of the ring seal 16 is elastically pressed to the cylindrical surface of the outdrive unit 1. Thus, a double seal arrangement is performed by the diaphragm seal 15 and the ring seal 16.
In the above arrangement, since the lower diaphragm seal 15 has the bent portion 15a projecting upward (or downward), and therefore has sufficient elasticity, the vibration of the engine is not transmitted to the hull 9 through the diaphragm seal 15. However, since the outer portion of the ring seal 16 is engaged into the groove 14a in the flange 14, and the inner portion thereof is strongly pressed to the outdrive unit 1, the ring seal 16 has less elasticity, which results in a disadvantage that the vibration of the engine is transmitted to the hull 9 through the ring seal 16.
In order to dissolve the above disadvantage, the applicant has developed a structure shown in FIG. 2, which is not the invention. In FIG. 2, an annular lip 16a is formed at the inner edge of the ring seal 16 fitted into the groove 14a in the seal flange 14. The lip 16a is pressed to the outer surface of the outdrive unit 1. In this structure, when the outdrive unit 1 swings forward or rearward by thrust during forward driving or reverse driving, a part of the soft lip 16a is further compressed and deformed, and another part may be parted from the outdrive unit 1. Therefore the ring seal 16 may not function as sealing means.
Accordingly, it is an object of the invention to provide an improved seal arrangement, overcoming the above-noted disadvantages, wherein both ends of an upper ring seal are fastened to an outdrive unit and an inner edge of an annular seal flange, respectively.
Another object of the invention is to detect water entered into the space between the upper ring seal and a lower diaphragm seal by means of a water sensor arranged therebetween and connected to warning means, when the lower diaphragm seal is torn or cracked.
Other and further objects, features and advantages of the invention will appear more fully from the following description of the preferred embodiments of the invention.